btf__base_btf
base = btf__base_btf(btf);
if (btf__base_btf(btf))
start_id = btf__type_cnt(btf__base_btf(btf));
old_base = btf__base_btf(src_btf);
if (btf__base_btf(btf)) {
LIBBPF_API const struct btf *btf__base_btf(const struct btf *btf);
r.dist_base_btf = btf__base_btf(btf);